Containers for corrosive food products

ABSTRACT

An aluminum food product container or can having an easily opened can end seamed to one end of the can body. The outer surface of the can end member has a score line along which the can end is severed for opening the can. The inner can end surface is coated with an enamel coating to withstand the corrosive attack of food products packed in the can. The undersurface area of the can end member beneath the score line is coated with a sealing compound material to prevent corrosive attack of the aluminum by the food product contents of the can where the enamel may have cracked incident to scoring the can end member.

United States Patent 1 1 1 1 McKernan Jan. 8, 1974 54] CONTAINERS FOR CORROSIVE FOOD 2,723,778 11/1955 Rabak 220/48 PRODUCTS 2,973,116 2/1961 Roberge 220/8l [75] Inventor: Bernard J. McKernan, Massillon, I

Ohio

[73] Assignee: Van Dorn Company, Cleveland,

Ohio [22] Filed: Sept. 9, 1970 [21] Appl. No.: 70,843

[52] US. Cl. 220/54, 220/53 [51] Int. Cl B65d 17/20 [58] Field of Search 220/54, 48, 64, 67, 220/81, 90.6

[56] References Cited UNITED STATES PATENTS 3,632,461 8/1972 Gayner .l 220/53 X 3,447,713 6/1969 Stec 3,463,348 8/1969 Pound et a1 220/90.6 X

Primary Examiner-George T. Hall Attorney-Frease and Bishop ABSTRACT An aluminum food product container or can having an easily opened can end seamed to one end of the can body. The outer surface of the can end member has a score line along which the can end is severed for opening the can. The inner can end surface is coated with an enamel coating to withstand the corrosive attack of food products packed in the can. The undersurface area of the can end member beneath the score line is coated with a sealing compound material to prevent corrosive attack of the aluminum by the food product contents of the can where the enamel may have cracked incident to scoring the can end member.

4 Claims, 4 Drawing Figures PATENTED JAN 8 I974 INVENTOR. Berna/10L J Mqferm 6 W & W

A 'l'TORNIu' YS 1 CONTAINERS FOR CORROSIVE FOOD PRODUCTS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to food product cans packed either hot or cold that are provided with can end members which may be opened easily by tearing a portion thereof along'a score line formed in the end member. Such food product cans including their bodies and end members desirably frequently are formed of aluminum. The inner surfaces of such aluminum can bodies and end members are coated with enamel to prevent any reaction between the aluminum and the contained food product, such as a corrosive attack of some food products upon aluminum.

2. Description of the Prior Art Prior containers of the type described have experienced a short shelf life of the canned food product. It has been discovered that the scoring of aluminum can end members to provide for easy opening by tearing out a portion of the end member along a score line produces hairline fractures of the enamel coating on the inner surface of the end member beneath the score line. This damage is inherent in any manufacturing procedure which involves scoring stock precoated with enamel. Furthermore, areas of stress in metals are predisposed to electrolytic corrosion.

Certain food products, usually those with a pH below 4.5, such as lemon pudding, applesauce, tomato products, and products acidulated with vinegar, citric, malic, or other acids react to produce corrosion along the enamel fractures early in the shelf life of such canned foods. The corrosion is characterized by excessive hydrogen formation and/or perforations along the score line.

Attempts have been made to avoid or delay the corrosive process by spraying enamel over the precoated interior enamel area of the end member where the fractures occur and baking the secondary or post-coated enamel thereon. Such procedure eliminates the corrosion problem but the material, processing, and labor costs are substantial so that such treatment is not economically justified.

SUMMARY Orrin; INVENTION Objectives of the invention include providing at minimum cost a protective coating over the vulnerable scored area of a can end member inner surface which prevents a corrosive reaction between the end member metal and the food contents of the can; forming the protective coating preferably of the same sealing compound as is used forsealing the double seamed joint between the can body and end member; applying the enamel fracture protective material to the inner can end surface beneath the scored area at the same time that the seam sealing compound is applied to the can end member blank; eliminating any requirement for baking enamel-type corrosionprotective material after being applied to the can end member; and thereby providing commercially "for economical protection of aluminum can end members from corrosive attack by certain foodproducts; and eliminating difficulties heretofore encountered, achieving the indicated objectives simply, effectively and inexpensively, and solving existing problems and satisfying existing needs in the canned food products field.

These objectives and advantages are obtained by the easy opening metal can and can end construction, the general nature of which may be stated as including an aluminum can end wall adapted to be seamed to the side walls of a metal can body by a usual double seam; the end wall having an inner surface provided with an enamel coating, and having a recessed end panel extending from a recessed corner, the corner being located below the seam; an end-panel-defining continuous score line formed in the end wall very close to the recessed corner; pull tab means secured to the end panel for tearing the end panel from the end wall; and a band of sealing compound applied and adhering to the inner surface of the end wall over the area thereof beneath the score line.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a can provided with the new construction;

FIG. 2 is a vertical section looking in the direction of the arrows 2-2, FIG. 1;

FIG. 3 is an enlarged sectional view of the can end before being seamed to the can body; and

FIG. 4 is a fragmentary sectional view on an enlarged scale of a portion of FIG. 3.

Similar numerals refer to similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is illustrated typically in the drawings applied to a small sized can although the can may be of any one of a number of standard sizes or capacities.

The can 1, generally of conventional construction, has a cup-shaped body with a bottom wall 2, and side walls 3, and a can end wall 4 connected by a usual double seam 5 to the upper or open end of the side walls 3. End wall 4 has a recessed corner 6 at the lower end of double seam 5 preferably seated on a ledge 7 formed adjacent the upper end of side walls 3, and a curved score line 8 is formed in the end wall 4 very close to the recessed corner 6. The score line 8 defines an end panel 9 which is completely removable from the remainder of the end wall 4 when torn or peeled along score line '8 to provide a fully opened top for the can 1.

A ring pull tab 10 preferably is connected by a rivet 1 l with the end panel 9 which may be made in any conventional manner or may be accomplished as set forth in Henning et al US. Pat. No. 3,346,948. Ring pull tab 10 preferably is formed of sheet metal of somewhat heavier gauge than the sheet metal from which can 1 and end wall 4 are formed. Members 1 and 4 are formed of aluminum. End wall 4'and ring pull tab 10 as thus far generally described may be made as shown in Henning et al US. Pat. No. 3,490,643.

In the usual manufacture of can end walls 4 such as shown in FIG. 3, the member is stamped from aluminum sheet or strip stock coated on one side with enamel. The coated side forms the inner surface of the end wall or end member 4 to protect that surface which has the exposed enamel coating thereon from attack by or reaction with the food product contained in the can. The can body similarly normally is formed from enamel coated aluminum sheet or strip stock.

In manufacturing the can end wall or member 4, the member is blanked from the coated aluminum stock,

generally to the shape illustrated in FIG. 3, except that the blank terminates in an outwardly extending flange indicated by dot-dash lines at 12. The blanked member then is passed through a curler which forms the curled flange 13 that subsequently becomes a part of the double seam 5. During another operation either before or after the curling operation, score line 8 is formed in the top or outer surface of the recessed portion of the end member 4 to define the end panel portion 9 which is subsequently to be removed.

After the curling operation, the usual seam sealing compound is deposited at 14 in the annular channel formed by the curled edge 13 and the recessed corner 6 which serves to seal the double sealed joint when the latter is formed- In accordance with the invention, sealing compound also is deposited at in an annular band of greater width than the cross-sectional contour of the score line 8 and located beneath and spanning the score line 8 and covering the enamel-coated inner surface of the end member 4 in an area extending circumferentially of the member 4 and radially inward and outward of the circumferential location of the score line 8, as shown in FIG. 4. This sealing compound band 15 beneath the score line 8 may be continuous with the seam sealing compound 14 or may be a separate band. Preferably the sealing compound is applied to the areas 14 and 15 at the same time so as to minimize the expense of applying the band 15. This sealing compound application can be carried out using two nozzles, one directed into the channel between the curl l3 and shoulder 6, and the other directed to the area beneath the score line 8.

Typical enamel coatings used for coating the inner surfaces of aluminum cans for food products are commercial materials known as Code No. S-9009-l02, a modified vinyl; Code No. 8-9009-105, a modified vinyl; Code No. S-9009-l 10, a modified vinyl; Code No. S- 9375-l09,.a modified epoxy; and Code No. 8-9364- 001, a modified epoxy; all products of Mobil Chemical Corporation of New York, New York. Another enamel sometimes used is Mark II, an organasol product of Dexter Midland Corporation of Waukegan, Illinois.

Sealing compounds that may be used for sealing the double seamed joints of aluminum food product cans and which also may be used in accordance with the invention to cover the area below the score line 8 include Code No. 3501 compound, a commercial product of Dewey & Almy Chemical Division of W. R. Grace & Co., Cambridge, Massachusetts.

Other typical sealing compounds that may be used either for the double seamed joint seal or the score line protective coating, or both, include Code No. 9101 which, like Code No. 3501, is a solvent'base synthetic rubber compound; Code No. B51, a water base synthetic rubber compound; and Code No. I-I-l5 75, a plastisol; all of which also are commercial products of Dewey & Almy chemical Division of W. R. Grace & Co.

The can body, although described above as being formed of aluminum, may be made of other metals such as steel, chemically treated steel, or tinplate, any of which may or may not have an enamel coating on that surface which is exposed to the food product contained in the body.

The indicated sealing compound may also. be described as a gasket-like material which adheres to the enamel-coated surface of the can end member 4 and the band l5'thereof covering the area beneath the score line 8 completely covers and protects any fracture in the enamel coating thatmay have occurred incident to scoring so that no corrosion will develop between corrosive food products and the aluminum.

Tests have shown that food products (applesauce) 'contained in cans such as illustrated in FIGS. 1 and 2 but without the potective band of sealing compound beneath the score line 8 exhibited failures due to corrosion after 6 months at F. of 15.8 percent of the cans tested, and 36.8 percent of the cans tested after 1 1 months.

Comparative tests of similar cans also containing applesauce but having the protective sealing compound 15 on the enamel-coated surface of member 4 beneath the score line 8 exhibited no failures under the same conditions after 13 months.

Another unexpected result is that the sealing compound material in the band 15 seems to stretch and spread and reduce the sharpness of the metal where scored after the end panel 9 is removed.

The improved construction eliminates the corrosion problem which has existed in the aluminum canned food products field in a very economic and practical manner .and, thus, provides a construction which achieves the objectives and solves problems existing in the art.

In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.

Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described since the features of the invention may be applied to different sized cans.

Having now described the features, discoveries and' principles of the invention, the manner in which the improved structure is made, the characteristics of the new construction, and the advantageous, new and useful results obtained; the new and useful structures, devices, elements, arrangements, parts combinations, and subcombinations are set forth in the appended claims.

I claim:

1. Easy opening metal food products can construction including a metal can body, a corrosion resistant aluminum can end wall, double seam means connecting the end wall to the can body; the end wall having a recessed comer-located below the seam, and having a recessed portion with outer and inner surfaces extending from said corner; an end-panel-defining continuous score line formed in the end wall metal at the outer surface of the recessed portion close to the recessed corner; pull tab means secured to the end panel for tearing the end panel from the end wall along said score line; the end wall inner surface being provided with an exposed enamel coating; and a band of sealing compound adhering to the inner enamel-coated surface of the end wall located beneath and spanning the score line and covering the enamel-coated inner surface area extending circumferentially of the end wall and radially inward and outward of the circumferential location of the score line to protect any fracture in the enamel coating beneath the score line, occurring incident to scoring,

located in the double seam means comprises the same sealing compound composition.

4. The construction defined in claim 1 in which the band of sealing compound extends along the inner enamel-coated end wall surface on those portions of the end wall that are located in the double seam means. 

1. Easy opening metal food products can construction including a metal can body, a corrosion resistant aluminum can end wall, double seam means connecting the end wall to the can body; the end wall having a recessed corner located below the seam, and having a recessed portion with outer and inner surfaces extending from said corner; an end-panel-defining continuous score line formed in the end wall metal at the outer surface of the recessed portion close to the recessed corner; pull tab means secured to the end panel for tearing the end panel from the end wall along said score line; the end wall inner surface being provided with an exposed enamel coating; and a band of sealing compound adhering to the inner enamel-coated surface of the end wall located beneath and spanning the score line and covering the enamel-coated inner surface area extending circumferentially of the end wall and radially inward and outward of the circumferential location of the score line to protect any fracture in the enamel coating beneath the score line, occurring incident to scoring, against the developement of corrosion between the end wall metal and can contents at such fracture.
 2. The construction defined in claim 1 in which sealing compound is provided extending over those portions of the inner enamel-coated end wall surface that are located in the double seam means.
 3. The construction defined in claim 2 in which the band of sealing compound and the sealing compound located in the double seam means comprises the same sealing compound composition.
 4. The construction defined in claim 1 in which the band of sealing compound extends along the inner enamel-coated end wall surface on those portions of the end wall that are located in the double seam means. 